Seismic modeling system providing seismic survey data frequency domain inpainting and related methods

ABSTRACT

A seismic modeling system may include a seismic model data storage device, and a processor cooperating with the seismic model data storage device to transform a seismic model spatial domain data set associated with a given region into a seismic frequency domain data set, where the given region includes a suspect region, transform a seismic model spatial domain data subset associated with the suspect region into a seismic frequency domain data subset, and perform inpainting of the seismic frequency domain data subset based upon the seismic frequency domain data set. The processor may further convert the inpainted seismic frequency domain data subset into an inpainted spatial domain data subset, and substitute the inpainted spatial domain data subset for the seismic model spatial domain data subset associated with the suspect region in the seismic model spatial domain data set associated with the given region.

TECHNICAL FIELD

The present invention relates to the field of data modeling, and, moreparticularly, to modeling systems such as seismic surveying and modelingsystems and related methods.

BACKGROUND

In sub-surface geological surveying, such as for oil and gasexploration, various approaches are used in an attempt to “see” belowground to help determine what is in the given geological formationbefore going to the expense of drilling an exploratory well. One suchapproach is to direct compressional or “P” waves at the geologicalsurface and measure the returns from the waves reflecting off ofdifferent materials in the ground. Another related approach is to useshear or “S” waves for this same purpose, which propagate through solidsonly.

Various difficulties may arise with such approaches when there areobstructions in the geological formation that cause distorted or nosignal returns for certain areas within the geological formation. Forexample, one such obstruction is gas clouds in a geological formation,which may distort the signature data returned, and/or make it appearthat certain areas (such as oil deposits) are located at the wrong depthin the formation. Thus, even knowing that there is an oil formationbeneath a gas cloud, it is still possible that a well being drilled maystill miss the deposit because of drilling to an incorrect depth.Moreover, there may be other types of obstructions in the formations(e.g., water pockets, basalt, volcanic rock layers, etc.) that may blocksignal returns altogether in some areas, resulting in incomplete datasets from P or S wave signal collection.

As such, advancements in correcting and/or filling missing data inseismic survey data sets may be desirable in certain applications.

SUMMARY

A seismic modeling system is provided which may include a seismic modeldata storage device, and a processor cooperating with the seismic modeldata storage device to transform a seismic model spatial domain data setassociated with the given region into a seismic frequency domain dataset, where the given region includes a suspect region. The processor mayalso transform a seismic model spatial domain data subset associatedwith the suspect region into a seismic frequency domain data subset, andperform inpainting of the seismic frequency domain data subset basedupon the seismic frequency domain data set. The processor may furtherconvert the inpainted seismic frequency domain data subset into aninpainted spatial domain data subset, and substitute the inpaintedspatial domain data subset for the seismic model spatial domain datasubset associated with the suspect region in the seismic model spatialdomain data set associated with the given region.

By way of example, the seismic model spatial domain data set maycomprise a compressional wave data set.

Furthermore, the processor may substitute the inpainted spatial domaindata set based upon a vertical correlation compensation.

In accordance with one example embodiment, the processor may inpaintbased upon an exemplar inpainting algorithm. In another exampleembodiment, the processor may inpaint by propagating contour data (e.g.,elevation and/or impedance data) along a direction of lines of constantcontour from adjacent portions of the seismic frequency domain data setinto the seismic frequency domain data subset. More particularly, thecontour data may include at least one of phase and amplitude data.Additionally, the processor may iteratively propagate the contour datainto the seismic frequency domain data subset.

In accordance with an example embodiment, the processor may performinpainting based upon at least one turbulent fluid flow modelingequation. By way of example, the at least one turbulent fluid flowmodeling equation may comprise at least one Navier-Stokes equation.

A related seismic modeling method may include using a processor totransform a seismic model spatial domain data set associated with agiven region into a seismic frequency domain data set, with the givenregion including a suspect region, transform a seismic model spatialdomain data subset associated with the suspect region into a seismicfrequency domain data subset, and perform inpainting of the seismicfrequency domain data subset based upon the seismic frequency domaindata set. The method may further include using the processor to convertthe inpainted seismic frequency domain data subset into an inpaintedspatial domain data subset, and substitute the inpainted spatial domaindata subset for the seismic model spatial domain data subset associatedwith the suspect region in the seismic model spatial domain data setassociated with the given region.

A related non-transitory computer-readable medium may havecomputer-executable instructions for causing a computer to perform stepsincluding transforming a seismic model spatial domain data setassociated with a given region into a seismic frequency domain data set,with the given region including a suspect region, transforming a seismicmodel spatial domain data subset associated with the suspect region intoa seismic frequency domain data subset, and inpainting the seismicfrequency domain data subset based upon the seismic frequency domaindata set. The steps may further include converting the inpainted seismicfrequency domain data subset into an inpainted spatial domain datasubset, and substituting the inpainted spatial domain data subset forthe seismic model spatial domain data subset associated with the suspectregion in the seismic model spatial domain data set associated with thegiven region.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of a seismic modeling system inaccordance with an example embodiment.

FIG. 2 is a 3D representation of a seismic model spatial domain data setfor a geographical region.

FIGS. 3a-8a are various vertical cross-sectional views of the seismicmodel spatial domain data set of FIG. 2 taken along line a-aillustrating a frequency domain inpainting operation by the system ofFIG. 1 in accordance with an example embodiment, and FIGS. 3b-8b arecorresponding lateral cross sectional views to those of FIGS. 3a-8ataken along line b-b in FIG. 2.

FIGS. 9A-9D are a series of close-up views of a void in a model data setillustrating a partial differential equation (PDE) inpainting techniquewhich may be used by the system of FIG. 1.

FIGS. 10A-10D are a series of close-up views of a void in a model dataset illustrating an exemplar inpainting technique which may be used bythe system of FIG. 1.

FIG. 11 is a flow diagram illustrating method aspects associated withthe system of FIG. 1.

FIG. 12 is a schematic block diagram of a seismic modeling system inaccordance with another example embodiment.

FIG. 13A is a cross-sectional view of a seismic model spatial domaindata set having a void therein caused by an obstruction, and FIG. 13B isa corresponding cross-sectional view to that of FIG. 13A after anexemplar inpainting operation by the system of FIG. 12.

FIG. 14 is a flow diagram illustrating method aspects associated withthe system of FIG. 12.

FIG. 15 is a schematic block diagram of a seismic modeling system inaccordance with still another example embodiment.

FIG. 16A is a cross-sectional view of a seismic model spatial domaindata set for a geographical region having a suspect region therein at afirst time, and FIG. 16B is a cross-sectional view of a seismic modelspatial domain data set for the geographical region with the suspectregion at a second time after the suspect region has moved, and whichmay be inpainted by the system of FIG. 15 based upon a comparison of thesuspect regions at the first and second times.

FIG. 17 is a flow diagram illustrating method aspects associated withthe system of FIG. 15.

FIG. 18 is a schematic diagram illustrating predictive error conceptanalysis and calibration operations which may be performed by the systemof FIG. 15 with the use of reference or truth data.

FIG. 19 is a schematic block diagram illustrating inpainting after thecalibration operations shown in FIG. 18 and without truth data.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present description is made with reference to the accompanyingdrawings, in which exemplary embodiments are shown. However, manydifferent embodiments may be used, and thus the description should notbe construed as limited to the particular embodiments set forth herein.Rather, these embodiments are provided so that this disclosure will bethorough and complete. Like numbers refer to like elements throughout.

Referring initially to FIG. 1, a seismic modeling system 30illustratively includes a seismic model data storage device 31 forstoring a seismic model spatial domain data set and a processor 32. Byway of example, the processor 32 may be implemented using a centralprocessing unit (CPU) or microprocessor of a PC, Mac, Sun, or othercomputing workstation, along with an associated non-transitorycomputer-readable medium having computer executable instructions forperforming the various operations described further herein.

The system 30 advantageously allows for regions of data in a seismicmodel data set that are partially corrupted, missing, or otherwisesuspect to be inpainted based upon data surrounding the suspect ormissing region. In the example illustrated in FIG. 1, a subsea datacollection approach is illustrated in which a vessel 35 utilizes aseismic airgun 36 and an array of audio monitors or transducers 37 forcompressional wave (P wave) seismic data collection of an underseageological formation. However, it should be noted that the techniquesdescribed herein may be used for land-based seismic survey data, andalso by other approaches than P wave data collection (e.g., seismic or Swave collection, etc.).

In the present example, below the ocean 38 there are various geologicallayers 39 a-39 c one on top of the other as shown. The geological makeupor constituency of the various layers 39 a-39 c will cause them to passor reflect different frequency signals. This is illustrativelyrepresented by signal lines 40 a, which correspond to a frequency thatcauses them to be reflected back towards the audio monitors 37 by thematerial(s) in the layer 39 b. Moreover, signal lines 40 b, whichcorrespond to a frequency that penetrates through the layers 39 a-39 cto an oil and gas deposit 41, are similarly reflected off the oil or gasdeposit back to the audio monitors 37. All of the audio signal frequencyreturns may then be used to create a time or spatial domain data set 43that maps the various frequency reflections to their respective depthsfor the surveyed region. By way of example, the data set may be storedin a SEG Y file format, although other suitable file formats may be usedin different embodiments. In some embodiments, the signal returninformation may be augmented with core sample data where suchinformation has been collected for the given geographical region,although this is not required in all embodiments.

However, in some instances there are obstructions, which in the presentexample is a gas cloud 42, that may interfere with the signal frequencyreturns. Generally speaking, a gas cloud may occur where there is apocket of gas that begins to permeate through a porous rock layer, etc.,and thus branches out away from the cavity where the original gas pocketis located. Such gas clouds may cover several kilometers in area, andmay move or migrate over time. As noted above, other examples ofobstructions may include water pockets, basalt, volcanic rock layers,etc.

Depending on the particular obstruction, the signal frequency returnsmay either be completely blocked so that no information is returned fora given region or portion of the area being surveyed, or the informationreturned for the given region is blurred or obscured. Moreover, in thesecases, it may appear that certain formations such as the oil and gasdeposit 42 are shifted down below where it is actually present withinthe formation. Such a “blurred” result is present in the data set 43 asa result of the gas cloud 42, as indicated by the rectangle 44. The datawithin the rectangle 44 is therefore considered to be suspect data, inthat its resolution indicates that there may be missing frequencyinformation for the given region within the surveyed area that makesthis particular part of the data set untrustworthy. The blurring may bedue to missing high frequency information, while the shifting down maybe due to acoustic velocity distortion.

Referring additionally to FIGS. 2-8 b and the flow diagram 110 of FIG.11, beginning at Block 111, the processor 32 may cooperate with theseismic model data storage device 31 to transform a seismic modelspatial domain data set 50 associated with a given region into a seismicfrequency domain data set 52 (e.g., via fast Fourier transform (FFT)),at Block 112. In this example, the given region includes a suspectregion bounded by a rectangle 51 in the data set, which is caused by anobstruction such as a gas cloud, as discussed above. In the presentexample, the suspect region was created by removing high frequencyreturn information from within the region bounded by the rectangle 51 sothat it would not only be blurred with respect to the surrounding data,but also vertically shifted to simulate the effects of a gas cloud. Inaddition, the processor 32 also transforms the subset of the data set 50that is associated with the suspect region (i.e., the area inside therectangle 51) into a seismic frequency domain data subset 53, at Block113.

The processor 32 may then perform inpainting of the seismic frequencydomain data subset 53 based upon the overall seismic frequency domaindata set 52, at Block 114. In the present example, the data set 52 andsubset 53 are magnitude spectrums of the spatial domain data set 50 andthe suspect region thereof, respectively, and for clarity of explanationreference to inpainting frequency data herein is with reference toinpainting the magnitude spectrum data. However, it will be appreciatedthat the corresponding phase spectrum data may in addition, or instead,be inpainted in the frequency domain in some embodiments, if desired,using the same techniques described herein for inpainting of themagnitude spectrum data.

The inpainting may be performed using various approaches. One suchapproach is a partial differential equation (PDE) based inpaintingapproach illustrated in FIGS. 9A-9D. Generally speaking, voids 141 a areinpainted in a data set by propagating contour data from outside a givenvoid into the given void. More particularly, seismic data may includeheight or elevation information as well as impedance information. Theprocessor 32 inpaints by propagating seismic contour data (e.g.,elevation and/or impedance information) from outside the given void 141a along a direction of lines of constant elevation contour from outsidethe given void into the void, as seen in FIGS. 9A-9D. More particularly,the lines of constant elevation contour may be based upon isophote(∇^(P)H) and gradient (∇H) directions at given points along the voidboundary, as shown in FIG. 9C. As will be appreciated by those skilledin the art, inpainting is a non-linear interpolation technique which inthe present example is used to propagate the data from the area around avoid created by an extracted building to “fill” the void.

More particularly, the processor 32 propagates elevation informationfrom outside the void along a direction of iso-contour, as representedby the following equation:

$\begin{matrix}{{\frac{\partial I}{\partial t} = {{\nabla L} \cdot N}},} & (1)\end{matrix}$where ∇L is a discrete Laplacian transform. An iso-contour direction Nis obtained by taking a 90 degree rotation of the gradient, as will beappreciated by those skilled in the art. An example inpainting equationfor performing the above-noted propagation is as follows:H ^(n+1)(i,j)=H _(n)(i,j)+ΔtH _(t) ^(n)(i,j),∀(i,j)∈Ω.  (2)

The above-noted propagation is performed a certain number of iterationsto “shrink” the void to a desired size as seen in FIG. 9D. The startingboundary 43 a of the void is shown in FIG. 9D so that the amount ofpropagation from one iteration may be seen. By way of example, severalthousand iterations of propagation may used for inpainting in a typicalseismic data inpainting application, although different numbers ofiterations may be used in different embodiments depending upon therequired accuracy and the computational overhead associated therewith.

Generally speaking, the above-described approach essentially treats thedata set to be inpainted as an incompressible fluid, which allows fluidmechanics techniques to be used for filling in the voids. That is, thepartial differential equations outlined above are used to estimate howthe boundaries directly adjacent a void in the data set would naturallyflow into and fill the void if the seismic data set was considered to bean incompressible fluid.

More particularly, with respect to the frequency domain (i.e., K space)data in the seismic data subset 53, the contour data corresponds to thephase and/or amplitude values of the data surrounding the voids. Hereagain, the propagation is preferably iteratively performed a desirednumber of iterations, or until a steady state is achieved.

Once again, this approach is based upon reconstructing data forfrequencies that are missing from a frequency domain representation of ageological area of interest by modeling the spectral signatures that arepresent in the data surrounding the voids as a turbulent (i.e., fluid)flow. That is, each individual known frequency is treated as a particlein an eddy flow, which are small turbulence fields inside of a generalturbulence field. As such, the known “eddies” in the frequency domaindata can therefore be modeled to interpolate the missing values.

Furthermore, in the illustrated example illustrated in FIGS. 5A and 5B,the magnitude spectrum data subset 53 is not completely void of allfrequencies, but rather will be missing one or more particular ranges offrequencies as a result of the obscured frequency returns caused by thesubterranean obstruction (e.g., the gas cloud 42). That is, otherfrequencies will still be present within the seismic data subset 53.Stated alternatively, in this seismic data inpainting example, the“voids” will be where the frequency data is incomplete. The presence ofsome frequency data within the suspect region will also serve as contourlines within the suspect region that will further guide the inpaintingof the missing frequencies, in addition to the lines of contour fromoutside of the suspect area as described above.

With respect to the frequency data inpainting, the processor 32 mayperform inpainting or seam smoothing based upon one or more turbulentfluid flow modeling equations. By way of example, Wavier-Stokes fluidmechanics equations/relationships may be used with some modification forK-space. More particularly, the stream function will have two componentsrather than one as follows:Ψ=A(k _(x) ,k _(y))e ^(zϕ(k) ^(x) ^(,k) ^(y) ⁾ =R(k _(x) ,k _(y))+zQ(k_(x) ,k _(y)),  (4)where the functions A, R, and Q are four times differentiable, andz=√{square root over (−1)}. Thus, looking at the derived equations withrespect to image intensities results in the following:

$\begin{matrix}{{{\frac{\partial}{\partial t}\left( {\nabla^{2}\Psi} \right)} + {\left( {v \cdot \nabla} \right)\left( {\nabla^{2}\Psi} \right)}} = {v{\nabla^{2}{\cdot {\left( {\nabla^{2}\Psi} \right).}}}}} & (5)\end{matrix}$

The iterative propagation described above results in an inpaintedseismic frequency data subset 54 (magnitude only in the currentexample). The above-described approach may accordingly allow forautonomous reconstruction of seismic data in places where obstructionscause the loss of some or all of the frequency data in a suspect region,yet while still retaining continuous elevation contours. Moreover, thenon-linear interpolation technique of inpainting allows for accuratepropagation of data from the area surrounding a void boundary. Further,the seismic data may advantageously be iteratively evolved until asteady state is achieved, and the speed of propagation may be controlledto provide a desired tradeoff between accuracy of the resultinggeospatial data and the speed so that the processing overhead burdendoes not become undesirably large.

The processor 32 may then convert the inpainted seismic frequency datasubset 54 into a “repaired” inpainted spatial domain data subset 55, atBlock 115, using an inverse FFT. The processor 32 may accordinglysubstitute the inpainted spatial domain data subset 55 for the seismicmodel spatial domain data subset associated with the suspect region(i.e., the area within the rectangle 51 in FIGS. 3A and 3B) in theseismic model spatial domain data set 50 to provide a repaired seismicspatial domain data set 56, at Block 116. This concludes the methodillustrated in FIG. 11 (Block 117). In some instances, a verticalcorrelation compensation may be used by the processor 32 when performingthe substitution so that the data subset 55 is properly aligned at thecorrect depth. Moreover, a seam-smoothing operation may optionally beperformed in some applications using a Navier-Stokes seam smoothingapproach, or a Poisson-based seam smoothing approach such as describedin U.S. Pat. No. 8,239,175 to Wivell et al., which is assigned to thepresent Assignee and is hereby incorporated herein in its entirety byreference.

While various PDE based approaches were described for inpainting above,it should be noted that the frequency domain data subset could also beinpainted using an exemplar based approach. Moreover, an approach whereboth types of inpainting are alternatively used on a same void may beused, such as described in U.S. Pat. No. 7,881,913 to Smith et al.,which is assigned to the present Assignee and is hereby incorporatedherein in its entirety by reference. Generally speaking, exemplarinpainting is a patch-based texture synthesis approach that has apriority scheme for strong gradients in the scene. Exemplar inpaintingfills in void regions, from the smallest to the largest (if more thanone), by systematically searching for the data that is the “best fit” inthe input data set. Unlike parametric approaches which have limitationsbased on the size of the void to be filled in and the smoothness, theexemplar method is well suited for removing large voids containing highfrequency data in a scene. As noted above, seismic data may includeheight or elevation information as well as impedance information, eitheror both of which may be inpainted using the techniques described herein.

Referring now to FIGS. 10A-10D, the exemplar algorithm is anisophote-driven image sampling process. There are several steps that gointo inpainting a region Ω. The boundary ∂Ω evolves inward, and thecontour ∂Ω is the fill front. The object is to obtain data fromsomewhere that will fill in the region Ω of missing data (i.e., thevoid). The source region Φ is chosen as the region from which the filldata will be obtained. It should be noted that the source region Φ maycome from different locations from within the image, or from otherimages, such as another data set for the geological region in question,in some embodiments.

To perform an iteration of exemplar-based inpainting, a point p is firstidentified. In the illustrated embodiment, a square template (i.e.,patch) is obtained about the point p, where the patch is designated asΨ_(p)∈Ω. A statistical approach is employed to find a patchΨ_({circumflex over (q)})∈Φ centered at {circumflex over (q)} which ismost similar to those parts already filled in Ψ_(p)∈Ω, as will beappreciated by those skilled in the art. It should be noted that thesearch space that is required to find the completely filled in templateΨ_({circumflex over (q)})∈Φ may be varied.

A potential drawback of template-based exemplar inpainting is itsability to handle linear features. Criminisi, et. al in a presentationentitled “Object Removal by Exemplar-based Inpainting,” June 2003Madison, Wis. Proc. IEEE Computer Vision and Pattern Recognition,describe a scheme for assigning patch priority. The order of filling inthe patches is significant. Criminisi et al. proposed that given a patchΨ_(p) centered at p for some p∈∂Ω, its priority P(p) is defined as theproduct of two terms, that is: P(p)=C(p)D(p). C(p) is the confidenceterm, and D(p) is the data term, which are defined as follows:

${{C(p)} = \frac{\sum\limits_{q \in {\Psi_{p}\bigcap\overset{\_}{\Omega}}}{C(q)}}{\Psi_{p}}},{and}$${{D(p)} = \frac{{{\nabla I_{p}^{\bot}} \cdot n_{p}}}{\alpha}},$where |Ψ_(p)| is the area of Ψ_(p), α is a normalization factor (e.g.255 for a typical gray value image), and n_(p) is the unit vectororthogonal to the front ∂Ω in the point p.

The priority is computed for every border patch, with distinct patchesfor each pixel on the boundary of the target region Ω. Duringinitialization, the function C(p)=0 ∀p∈Ω, and C(p)=1 ∀p∈I−Ω. Theconfidence term C(p) can be thought of as a measure of the amount ofreliable information (i.e., pixels) surrounding the point p. The goal isto first fill in pixels in those patches which have more of their pixelsalready filled, with additional preference given to pixels that werefilled in earlier. The term D(p) is a function of the strength of theisophotes hitting the front ∂Ω at each iteration. The term encouragespatches that contain linear features to be filled in first along thefront. Therefore, this algorithm encourages a patch-based infillingtechnique that handles structural and high-frequency content at the sametime.

Turning to FIGS. 12-14, another example seismic inpainting applicationwhere such an exemplar inpainting approach may be particularlyadvantageous is now described. Similar to the prior application, subseacompressional wave (P wave) seismic data collection is perform by thevessel 35 utilizing the seismic airgun 36 and audio monitors 37.However, in this case, the obstruction 242 above the oil and gas deposit41 is not a gas cloud, but instead is an underground “lake” or waterconcentration. Such obstructions may block some, if not all, frequenciesfrom passing therethrough to the oil and gas deposit 41 below, whichresults in a void 121 in a returned seismic model spatial domain dataset 120 (e.g., P Wave data set) corresponding to the area or regionbelow the obstruction 242. In the example of FIGS. 12 and 13A, data wasremoved from within the rectangle in the data set 120 to simulate such asuspect area as the void 121.

Beginning at Block 141 of the flow diagram 140, the processor 32 mayidentify the obstruction 121 within the seismic model spatial domaindata set 120 having a lateral boundary, at Block 142, and define asuspect area (here the area within the rectangle) including spatialdomain data within the lateral boundary and directly below theobstruction, at Block 143. More particularly, the processor 32 maydetermine the vertical depth at which the top of the obstruction ispositioned, as well as the lateral outline or boundary of theobstruction, and this shape may be projected downward through thegeological formation to define the suspect area within this 3D volume asthe void 121 to be inpainted. This may be an irregularly shaped volume,or in some embodiments such as the one illustrated in FIGS. 12 and 13A,a rectangular cuboid (or other shapes such as a cylinder, etc.) may beused to define the void 121.

The processor 32 may then inpaint the suspect area in the seismic modelspatial domain data set 120 based upon an exemplar inpainting algorithmor approach, such as the one described above, at Block 144, whichillustratively concludes the method illustrated in FIG. 14 (Block 145).An inpainted seismic spatial domain data set 122 which results frominpainting of the void 121 in the original seismic spatial domain dataset 120 is shown in FIG. 13B. As described above, the inpainting may beperformed iteratively until a stopping value associated with the givenvoid is at a steady state or below an error threshold, for example.Moreover, in some embodiments, a pre-conditioning of the data may beperformed prior to inpainting, such as a pre-stack migration signalprocessing enhancement. Additional pre-conditioning may include phaseunwrapping in order to ensure that all appropriate multiples of 2 pi (π)are included when processing the phase response.

Turning now to FIGS. 15-18, with respect to obstructions such as gasclouds in a geological formation, the boundaries of the gas clouds maychange over time, either by a migration of the cloud within theformation or a change in the volume or shape of the cloud. One suchexample is illustrated in FIGS. 15-16B, in which at a first time t₁ anobstruction (e.g., gas cloud) results in a suspect region 131 in a firstseismic spatial domain set 130, but at a second time t₂ the suspectregion has moved to a different location in a second seismic spatialdomain data set 132. In such cases, valuable information may bedetermined by comparing data which was originally obscured (i.e., in thesuspect region) in the first data set 131, but is no longer within thesuspect region in the second data set 132, and such information may beused to train the inpainting of the suspect region in the second dataset.

To provide such training for inpainting, the processor 32 may providefor autonomous change detection of subterranean voids or suspectregions. More particularly, beginning at Block 171 of the flow diagram170, the processor 32 may cooperate with the seismic model data storagedevice 31 to determine a first 3D boundary around the suspect region 131within the first seismic model spatial domain data set 130 for aparticular geological formation at the first time t₁, at Block 172, anddetermine a second 3D boundary around the suspect region within thesecond seismic model spatial domain data set 132 for the geologicalformation at the second time t₂ after movement of the suspect region, asdescribed above (Block 173). The processor 32 may then compare thesecond 3D boundary to the first 3D boundary to determine an overlappingportion OP where the first and second 3D boundary regions overlap, andone or more non-overlapping portions NOP1, NOP2 where the first andsecond boundaries do not overlap, at Block 174. In the illustratedexample, the suspect region 131 has migrated from left to right betweenthe time t₁ at which the first data set 130 was captured and the time t₂when the second data set 132 was captured. Thus, the non-overlappingportion NOP1 which was obscured at time t₁ is no longer obscured.Moreover, the second non-overlapping portion NOP2 has become obscured atthe time t₂, but it was not obscured at the time t₁.

The boundary comparison may be performed using various approachesincluding: root mean squared error (RMSE); center of mass; mutualinformation; differing 3D boundary voxels; motion; volume change; andsurface area change. Motion of a gas cloud over time may be determinedby a mean absolute error (MAE), mutual information, or content change.

More particularly, with respect to an RMSE comparison, a relative erroris determined to measure a change within the seismic data. RMSE iscomputed by comparing each point in the first seismic data set 130 withthe nearest point in the second seismic data set 132. An RMSE value nearzero (or below a threshold value) indicates nearly identical 3D model orobjects, which thereby allows for a direct measure of variation at thegiven point.

Regarding mutual information as a measure of change or similarity,mutual information is defined as:I(X;Y)=H(X)+H(Y)−H(X,Y),  (1)where I is mutual information and H is entropy (see eq. (2) below). Thevectors X and Y correspond to histograms of seismic volume. When thedata vectors are more similar, a higher numerical value is obtained.Entropy is defined as:H(p _(i))=−Σp _(i) log(p _(i)),  (2)where p is the probability vector assumed to be a uniform distribution.

With respect to a center of mass comparison, the center of mass of a 3Dsolid is the unique point where the weighted relative position of thedistributed mass sums to zero. The density of a solid 3D object at agiven point may be determined with ρ(x,y,z) being the density (mass perunit volume) of an object occupying a region D in space. The integralover D gives the mass of the object. More particularly, if the object ispartitioned into n mass elements, when summing these mass element up,the total mass M is as follows:

$M = {{\lim\limits_{n\rightarrow\infty}{\sum\limits_{k = 1}^{n}{\Delta\; m_{k}}}} = {{\lim\limits_{n\rightarrow\infty}{\sum\limits_{k = 1}^{n}{{\delta\left( {x_{k},y_{k},z_{k}} \right)}\Delta\; V_{k}}}} = {\int{\int{\int_{a}^{b}{{\delta\left( {x,y,z} \right)}{dV}}}}}}}$The integral of ρ(x,y,z) gives the mass of the object:M=∫∫∫ _(a) ^(b) δdVwhere ρ(x,y,z) is the density at point (x,y,z).

For volumetric processing, the suspect area may be divided into aplurality of “volume slices”, to which optional removal processing maybe performed in some embodiments. A 3D edge detection may then beperformed on the volume slices, followed by a 3D blob filtering to buildand select respective models for the volume slices. The slices may thenbe converted to an overall volume for the suspect area, and a voxelcount may be compared as to the different volumes at times t₁ and t₂,for example.

The processor 32 may accordingly inpaint the overlapping portion OP inthe second seismic model spatial domain data set 132 based upon one orboth of the non-overlapping portions NOP1, NOP2 in the second seismicmodel spatial domain data set 132, at Block 175, which illustrativelyconcludes the method of FIG. 17 (Block 176). In this and theabove-described embodiments, the inpainted or repaired data sets may bestored and subsequently viewed on a display screen or printed forfurther analysis as desired.

The non-overlapping portion NOP2 need not be inpainted, as thecorresponding “truth” data from the first data set 130 may besubstituted for the void or missing data that is present in the seconddata set 132. Yet, the truth data from one or both of thenon-overlapping portions NOP1, NOP2 may advantageously be used to trainthe inpainting of the overlapping portion OP to provide improvedaccuracy.

For the present example, the above-described exemplar inpainting methodwith Poisson Merging may be used for inpainting the void in theoverlapping portion OP, although a PDE-based approach (or a combinationof the two) may also be used. Initially, the suspect region 131 may beinpainted in the first data set 130 using initial starting parameters,and the inpainted portion of the suspect region corresponding to thenon-overlapping portion NOP1 may be considered as sample set for thefollowing discussion. With the sample set filled, the error may becalculated with respect to the truth data. For each void (sample), anerror value is calculated and recorded. The standard RMSE between thetruth data (i.e., the non-overlapping portion NOP1 of the data set 132),and the results of the candidate fill algorithm is calculated. This iscomputed on a void by void basis, resulting in a unique error for eachvoid. This compilation forms an error report.

To properly predict error for new samples, it is generally desirable toexamine the characteristics of the voids. Moreover, a good set ofdescription metrics that may be used for this purpose may be defined.The goal for these metrics is to predictively model the variation in thedifference between the fill results and the truth data (i.e., theerror). The collection of metrics may be calculated for the void(s) inthe sample set. The output may be a report detailing these calculatedmetric values on a void by void basis.

Given a relatively large collection of available metrics, there is agood chance that many of them may not be needed for prediction. That is,there may be elements that contain redundant information, which isindicated by a high degree of mutual correlation. The other types ofmetrics that may be eliminated from the set are those that are found tonot contain enough relevant information for the task of prediction(i.e., those whose values tell nothing about the expected output which,in this case, is error). To guard against metrics in the formercategory—those with redundant information—correlation analysis may beused. Metrics are grouped with others where overlap may occur. Todetermine the amount of redundancy, metrics may be tested against eachother to determine their correlation. Those that are highly correlatedmay remain in a group together. Those that are not may be safelyseparated. The metric that best correlates with the error may taken fromeach group.

A statistical test may be used to determine which metrics fall into thesecond category mentioned above—those that do not contribute to theprediction—to prevent them from being placed into the final metricssubset. To accomplish this, hypothesis testing may be performed, asdetailed below. A linear regression may be run with the full subset ofcandidate metrics to define the prediction model that would result ifthis were the final metrics subset. From this regression, each metricreceives a coefficient value that describes the relationship between itand the value being predicted (in this case, error). Next, a hypothesisis determined that will allow the elimination metrics. Morespecifically, for each metric it is hypothesized that its coefficientvalue is actually zero (i.e., no relationship exists, and it istherefore useless in prediction). This allows use of the sample set ofdata to test the likelihood that the calculated coefficient could havebeen attained if the hypothesis were true. If the metric correspondingto the coefficient in question is significant, there will be a lowprobability that the calculated coefficient value would have occurred bychance. Following a standard statistical threshold for any metric with avalue below 5%, the hypothesis is rejected and the metric is consideredsignificant for prediction. In this fashion, metrics are removed one ata time. This iterative removal may be desirable because the interactionsbetween metrics change as they are added and removed.

The prediction model may be independently validated on a set of datathat is separate from trained system data in order to properly assessthe model's ability to predict. To accomplish this, the selected sampledata set with corresponding truth data are split into a training set anda validation set with no overlap between them. Each sample (void) isexamined from the selected cells with all required information beingrecorded. These recorded entries are the actual values that are splitand recorded in the separate sets.

A good representation of the collection of voids is desirably presentedto the statistical prediction model. This requires that there be asufficient amount of sample voids with some form of corresponding truthdata available. This set of truth data is split into two parts: thetraining set and the validation set. This training dataset may now beused to find the optimal (or near optimal) values for the parametersthat make up the statistical prediction system, a process known astraining the system. FIG. 18 shows this process visually.

More particularly, the value of the void fill depends on how accuratelythe fill estimates or approximates truth (i.e., reference) data for thevoid region. The computation of the accuracy of void fill may not bepossible where void fill techniques are used that do not require truthdata for the void regions. However, an error associated with the voidfill may be estimated based on prior knowledge of how the giventechnique performs with voids where truth data is available.

Moreover, to build a model for estimating the error in a void fill, voidcomplexity predictor metrics may first be defined based oncharacteristics of the void perimeter. These metrics may include avariety of measures of the complexity of the void. One example of a voidcomplexity predictor metric is a measurement of the frequency of thedata surrounding the void.

A training phase is defined where data is collected for a suite of voidcomplexity predictor metrics for each void. The predictors may then bestatistically correlated and calibrated using truth data to determinewhich are the best predictors of fill accuracy, as shown in FIG. 18. Thecalibrated predictors are then used for estimating the accuracy of fillsfor fill regions without truth data, as shown in FIG. 19, whichillustrates the fill predictive (bounded) error concept application to acell with no truth data, i.e., the overlapping portion OP in the presentexample.

Using the training set described above, a form of linear regressionanalysis may be performed to fit the prediction model to the populationof voids. To do this, the set of the best description metrics available(those left after the iterative removal process previously discussed)may be combined to create a linear prediction equation. The performanceof this method during validation (described below) determines if thisstatistical method may properly describe the current problem domain orif another method should be used.

The goal of this step, regardless of the form of the prediction equationused, is to determine the coefficients of each parameter present. Thereis one parameter each per selected metric in the linear model, and thesecoefficients model the relationship between the metrics and the error.These optimal coefficients minimize a certain residual between thepredicted fill error and the actual fill error for the given trainingset in the given model. With the foregoing in place, error may now bepredicted for any new void sample for which the same selected metricvalues can be calculated

Validation provides a way to assess the performance of the newly createdmodel before applying it to the full application data set that has nocorresponding truth data. As previously mentioned, this process isperformed on a separate validation set that is not included during thetraining process. To validate the model, each sample in the validationset may be evaluated using the prediction model to produce a predictederror for each void. Along with this, confidence intervals may becalculated to further enhance the information contained in thiscalculation. The difference between the predicted value and the trueerror for the sample gives the error residual. The better the predictionmodel, the lower these values will be.

If these residual values indicate that the model does not sufficientlyfit the true behavior of the current problem domain, then a change isappropriate. Once an acceptable model is generated and validated, it isready for use in prediction of fill results for the full applicationdata set. At this point, the validation dataset is used to test theperformance of the current model. Since truth data is available, ananalysis may be made to determine how closely the model successfullypredicted the true error of the fill. Finally, with the model trainedand validated, the error that will occur in filling new samples withouttruth data may be predicted. Typically, these types of predictions mayinclude some form of confidence information along with the expectedvalue. The training and validation operations are illustrated in FIG.19.

A description of an example set of selected metrics set is now provided.These metrics and their corresponding beta values resulted from applyingthe described methodology on a selected set of training data andcandidate metrics. The selection of these metrics, from the originallist of metrics considered, is based on the statistics of the void data.The statistical analysis process not only selected this set ofpredictors, but also determined the number of predictors to use (i.e.,the system need not be asked for the top seven predictors, but ratherfor an optimal set under the current method) based on iterative analysisof the training results. In this example configuration, the selectedmetrics are based on the following: (1) average void diameter; (2)average impedance and slope differences on opposite sides of the void;(3) average impedance and slope differences on adjacent void posts; and(4) maximum impedance difference on void boundary for opposite andadjacent points. These metrics and their corresponding beta valuesresulted from applying the described methodology to the selected set oftraining data and candidate metrics. The predictive model thatincorporates these metrics is a multiple regression that has thefollowing form:Predicted Error=β1*X1+β2*X2+ . . . +β7*X7+Error Intercept.

The values of β (and the error intercept) are the model coefficientsobtained from the training and validation data sets, and the values of Xare the corresponding metrics. These are the subset of metrics selectedfrom an original collection of approximately fifty metrics. Theselection of these metrics is based on the statistics of the void data.The statistical analysis process not only selected this set ofpredictors, but also determined the number of predictors to use based onthe iterative analysis of the training results. The selected predictorsare as follows:

-   -   X1=Grid Avg Distance: For each point adjacent to a void        (boundary point), accumulate distance across the void in each        primary direction and divide by total number of such distances.    -   X2=Grid Stat: similar to the previous predictor, compute average        distance and average impedance difference between points across        void and sum the two averages.    -   X3=Avg Dir Range: for each void boundary post, maintain a Max        and Min neighbor elevation difference for each direction (8        possible directions, direction 0=north). Compute average        Max[dir]−Min[dir] of the pairs of stored values. Compute        impedance difference between blue post, and each neighbor,        saving the value if a new maximum or minimum value is found.        After processing all boundary posts, average the difference in        the pairs of Max and Min values.    -   X4=Slope Change %: order the boundary posts in a contiguous        clockwise fashion around the void. Compute impedance change        between consecutive posts. When consecutive impedance changes        differ by more than 50% of grid spacing, increment a counter.        After processing all impedance change pairs, divide by number of        boundary posts.    -   X5=Avg Opposite Slope: order the ‘n’ boundary posts in a        contiguous fashion. for first n/2 points, accumulate slope        between point(i) and point(i+n/2). Divide by n/2 for average.    -   X6=Max Opposite Delta: order the ‘n’ boundary posts in a        contiguous fashion. For first n/2 points, find maximum impedance        difference between point(i) and point(i+n/2).    -   X7=Elevation Extent: find the highest and lowest boundary post        values. Subtract lowest from highest to get the elevation        extent.        Further details regarding this approach may be found in Yates et        al., “Void Fill Accuracy Measurement and Prediction Using Linear        Regression”, ASPRS 2012 Annual Conference, March 2012, which is        hereby incorporated herein in its entirety by reference.

The above-described boundary tracking approach advantageous provides forprogressive predictive analtic precision, in that the boundary motiontracking enables retrospective model validation with new truth data.Moreover, this approach may be implemented using general purposecomputing on graphics processing units (GPGPU) to provide real orsubstantially real time 3D processing, along with the ability to workwith relatively large and complex seismic data sets. As such, this mayprovide a predictive framework to enhance resource (e.g., oil and gas)production based upon changes between subsequent measurements.

Additional background on the above-described techniques may be found inU.S. Pat. No. 7,760,913 to Rahmes et al.; U.S. Pat. No. 7,750,902 toRahmes et al.; U.S. Pat. No. 7,764,810 to Rahmes et al.; U.S. Pat. No.7,391,899 to Rahmes et al.; U.S. Pat. No. 7,528,938 to Garceau et al;U.S. Pat. No. 7,603,208 to Garceau et al.; and U.S. Pat. No. 8,855,427to Yates et al., which are assigned to the present Assignee and are allhereby incorporated herein in their entireties by reference.

Many modifications and other embodiments will come to the mind of oneskilled in the art having the benefit of the teachings presented in theforegoing descriptions and the associated drawings. Therefore, it isunderstood that the disclosure is not to be limited to the specificembodiments disclosed, and that modifications and embodiments areintended to be included within the scope of the appended claims.

That which is claimed is:
 1. A seismic modeling system comprising: aseismic model data storage device; and a processor cooperating with saidseismic model data storage device to transform a seismic model spatialdomain data set associated with a given region into a seismic frequencydomain data set, the given region including a suspect region, transforma seismic model spatial domain data subset associated with the suspectregion into a seismic frequency domain data subset, perform inpaintingof the seismic frequency domain data subset based upon the seismicfrequency domain data set, convert the inpainted seismic frequencydomain data subset into an inpainted spatial domain data subset,substitute the inpainted spatial domain data subset for the seismicmodel spatial domain data subset associated with the suspect region inthe seismic model spatial domain data set associated with the givenregion to generate an inpainted seismic model spatial domain data set,and store the inpainted seismic model spatial domain data set in theseismic model data storage device.
 2. The seismic modeling system ofclaim 1 wherein the seismic model spatial domain data set comprises acompressional wave data set.
 3. The seismic modeling system of claim 1wherein said processor substitutes the inpainted spatial domain data setbased upon a vertical correlation compensation.
 4. The seismic modelingsystem of claim 1 wherein said processor inpaints based upon an exemplarinpainting algorithm.
 5. The seismic modeling system of claim 1 whereinsaid processor inpaints by propagating contour data along a direction oflines of constant contour from adjacent portions of the seismicfrequency domain data set into the seismic frequency domain data subset.6. The seismic modeling system of claim 5 wherein the contour datacomprises at least one of phase and amplitude data.
 7. The seismicmodeling system of claim 5 wherein said processor iteratively propagatesthe contour data into the seismic frequency domain data subset.
 8. Theseismic modeling system of claim 1 wherein said processor performsinpainting based upon at least one turbulent fluid flow modelingequation.
 9. The seismic modeling system of claim 8 wherein the at leastone turbulent fluid flow modeling equation comprises at least oneNavier-Stokes equation.
 10. The seismic modeling system of claim 1comprising a seismic source and at least one seismic transducercooperating therewith to generate the seismic frequency domain data set.11. A seismic modeling system comprising: a seismic model data storagedevice; and a processor cooperating with said seismic model data storagedevice to transform a seismic model spatial domain data set associatedwith a given region into a seismic frequency domain data set, the givenregion including a suspect region, and the seismic model spatial domaindata set comprising a compressional wave data set, transform a seismicmodel spatial domain data subset associated with the suspect region intoa seismic frequency domain data subset, perform inpainting of theseismic frequency domain data subset based upon the seismic frequencydomain data set, convert the inpainted seismic frequency domain datasubset into an inpainted spatial domain data subset, substitute theinpainted spatial domain data subset for the seismic model spatialdomain data subset associated with the suspect region in the seismicmodel spatial domain data set associated with the given region basedupon a vertical correlation compensation to generate an inpaintedseismic model spatial domain data set, and store the inpainted seismicmodel spatial domain data set in the seismic model data storage device.12. The seismic modeling system of claim 11 wherein said processorinpaints based upon an exemplar inpainting algorithm.
 13. The seismicmodeling system of claim 11 wherein said processor inpaints bypropagating contour data along a direction of lines of constant contourfrom adjacent portions of the seismic frequency domain data set into theseismic frequency domain data subset.
 14. The seismic modeling system ofclaim 11 comprising a seismic source and at least one seismic transducercooperating therewith to generate the seismic frequency domain data set.15. A seismic modeling method comprising: using a processor and anassociated seismic model data storage device to transform a seismicmodel spatial domain data set associated with a given region into aseismic frequency domain data set, the given region including a suspectregion, transform a seismic model spatial domain data subset associatedwith the suspect region into a seismic frequency domain data subset,perform inpainting of the seismic frequency domain data subset basedupon the seismic frequency domain data set, convert the inpaintedseismic frequency domain data subset into an inpainted spatial domaindata subset, and substitute the inpainted spatial domain data subset forthe seismic model spatial domain data subset associated with the suspectregion in the seismic model spatial domain data set associated with thegiven region to generate an inpainted seismic model spatial domain dataset, and store the inpainted seismic model spatial domain data set inthe seismic model data storage device.
 16. The method of claim 15wherein the seismic model spatial domain data set comprises acompressional wave data set.
 17. The method of claim 15 wherein theprocessor substitutes the inpainted spatial domain data set based upon avertical correlation compensation.
 18. The method of claim 15 whereinthe processor inpaints based upon an exemplar inpainting algorithm. 19.The method of claim 15 wherein the processor inpaints by propagatingcontour data along a direction of lines of constant contour fromadjacent portions of the seismic frequency domain data set into theseismic frequency domain data subset.
 20. The method of claim 15comprising using a seismic source and at least one seismic transducercooperating therewith to generate the seismic frequency domain data set.21. A non-transitory computer-readable medium having computer-executableinstructions for causing a computer, comprising a processor and anassociated seismic model data storage device, to perform stepscomprising: transforming a seismic model spatial domain data setassociated with a given region into a seismic frequency domain data set,the given region including a suspect region; transforming a seismicmodel spatial domain data subset associated with the suspect region intoa seismic frequency domain data subset; inpainting the seismic frequencydomain data subset based upon the seismic frequency domain data set;converting the inpainted seismic frequency domain data subset into aninpainted spatial domain data subset; substituting the inpainted spatialdomain data subset for the seismic model spatial domain data subsetassociated with the suspect region in the seismic model spatial domaindata set associated with the given region to generate an inpaintedseismic model spatial domain data set, and storing the inpainted seismicmodel spatial domain data set in the seismic model data storage device.22. The non-transitory computer-readable medium of claim 21 wherein theseismic model spatial domain data set comprises a compressional wavedata set.
 23. The non-transitory computer-readable medium of claim 21wherein substituting comprises substituting the inpainted spatial domaindata set based upon a vertical correlation compensation.
 24. Thenon-transitory computer-readable medium of claim 21 wherein inpaintingcomprises inpainting based upon an exemplar inpainting algorithm. 25.The non-transitory computer-readable medium of claim 21 whereininpainting comprises inpainting by propagating contour data along adirection of lines of constant contour from adjacent portions of theseismic frequency domain data set into the seismic frequency domain datasubset.
 26. The non-transitory computer-readable medium of claim 21wherein the seismic model spatial domain data set is generated by aseismic source and at least one seismic transducer cooperatingtherewith.